Mercury switches



Jan. 1, 1957 L. MITCHELL 2,776,351

MERCURY SWITCHES Filed May 10, 1954 .v I 30 a I 2 .2! I "I I? V I I 34-r z lllll J IIIIIHIIIIII iNSUL'LATION 1.. I I

9 7 I. I I g is GLASS i mvmc L.M|TCHELL' I. 2/ f BY W0! W ATTORNEYINVENTOR United States Patent MERCURY SWITCHES Irving L. Mitchell,Rockville Centre, N. Y. assignor to Ebert Electronics Corporation,Queens Village, N. Y., a corporation of New York Application May 10,1954, Serial No. 428,535

Claims. (Cl. 200-112) The present invention relates generally to mercuryswitches, and more particularly to systems of multiple mercurydisplacement switches, having novel actuating coils.

It is known in the prior art to provide mercury displacement switchesincluding a vitreous envelope, containing a pool of mercury permanentlyin contact with one lead of an electrical circuit, and a further leadwhich may be brought into and out of circuit with the first mentionedlead by varying the level of the mercury pool. The level of the mercurypool many be raised or lowered by means of an electro-magneticallyactua'ble plunger, the latter being actuated from externally of thevitreous envelope in response to electrical energization of an actuatingcoil. Switches of the character described are commonly employed to makeand break two phase or three phase lines, one switch being employed ineach line, and a common actuating coil being employed for actuating thearmatures of the several switches.

In designing actuating coils for multiple mercury switches, the generalpractice has been to provide coils of circular cross-section, asymmetrical shape being desirable in order that the several armatures besymmetrically disposable with respect to the coil, and therebysynchronously operable, and further for reasons of simplicity andeconomy of winding. It is found, however, that coils of circularcross-section have extremely high leakage with respect to the switcharmatures, so that either a large coil current is required to securehigh velocity of switch operation, or a large number of coil turns.

In accordance with the present invention the actuating coil for amultiple mercury switch is arranged to have a cross-section whichminimizes leakage, maximizes actuating force on the switch armatures,assures symmetry of this force at the several armatures, reduces thetotal quantity of coil copper required, and yet which retains thesimplicity and economy of fabrication inherent in coils of circularcross-section.

In the case of a double switch assembly I employ an actuating coilcross-section having rounded ends which snugly fit the contour of theswitch containers, the rounded ends being joined by rectilinearelements. The total circumference of the coil cross-section is therebyminimized, and its coupling with the switch armatures maximized.

In the case of a triple switch, intended for use in a three phasecircuit, a similar expedient is employed, leading to generallytriangular coils, which are symmetrical in crosssection, employ aminimum of copper, and the coupling of which to the three switcharmatures is maximized and symmetrical.

It is, accordingly, an object of the present invention to provide anovel multiple mercury switch assembly, having an actuating coil whichis symmetrical with the several switches, the coupling of the coil withthe switch armatures being maximized, and the quantity of copper in thecoil minimized.

It is a more specific object of the invention to provide a three phasemercury switch assembly employ-ing three discrete mercury displacementswitches, in which a common actuating coil for the switches is ofgenerally triangular cross-section, the switches being located withinthe apices of the triangular cross-section.

It is a more general object of the present invention to provide anoperating coil for a plurality of mercury displacement switches, inwhich the coil is in maximum proximity to the switch envelopes.

It is a further general object of the invention to provide a novelactuating coil for multiple mercury displacement switches in which thecoil includes curvilinear portions, each partially embracing one of theswitches, and joined by relatively rectilinear portions, whereby aneconomically fabricated coil, of simple configuration, provides maximumforce at the armatures of the switches.

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of a specific embodiment thereof,especially when taken in conjunction with the accompanying drawings,wherein:

Figure 1 is a view in elevation, partially in crosssection, of a switchassembly including two mercury displacement switches;

Figure 2 is a view in elevation of a switch assembly including threemercury displacement switches;

Figure 3 is a view in plan of the system of Figure 1;

Figure 4 is a view in plan of a three switch system, in accordance withFigure 2; and

Figure 5 is a view in plan of a modification of the system of Figure 4.

Referring now more particularly to Figures 1 and 3 of the accompanyingdrawings, the reference numeral 1 denotes a first mercury displacementswitch and the reference numeral 2 a duplicate switch. The switches 1and 2 are arranged with their longitudinal axes parallel, within anoperating coil 3.

Describing the structure of the switch 1, as typical of the severalswitches employed in the practice of my invention, the switch 1 includesa vitreous envelope 5, having generally cylindrical longitudinal walls,an upper end wall 6, and a lower end wall 7. Extending through the lowerend wall 7 is a vitreous column 8, through which extends a lead 9. Thecolumn 8 terminates at its upper end in a hollow vitreous cup 10, intowhich the lead 9 extends,

" and the lead 9 extends externally of the envelope 5 in the form of aninsulated wire 11.

A second lead 12 extends internally of the lower end wall 7 intopermanent contact with a body of mercury 13, and extends externally ofthe envelope 5 in the form of an insulated wire 14.

extending nubs 19, which ride on the interior surface of the vitreousenvelope 5, and serve to guide the movement of the armature 16 parallelto its longitudinal axis. Coil springs 20 and 21 encompass the upper andlower end portions of the interior insulating sleeve 17, and extendbeyond the limits of the latter. The springs 20 and 21 serve to take upshock due to violent translation of the armature 16 during energizationof the armature 16.

The mercury pool 13 extends, in the open position of the switch, to alevel below the cups 10, and the armature 16 may be in its upperposition, all as illustrated in Figure 1 of the accompanying drawings.The armature 16 may be caused to move to a lower position, in responseto current flow in the coil 3, and in so moving displaces mercury,causing the level of the mercury to rise sufficiently to overflow thecup 10, thereby completing a circuit between lead 9 and lead 12, throughthe mercury.

When the coil 3 is de-energized the armature 16 ascends, and the circuitis broken.

It will be clear that the armature 16 may be sufiiciently weighted thatits normal position will serve to close the circuit, in which case thecoil 3 may be so located as to cause the armature 16 to rise, whenenergized, and thus to break the circuit.

The switches 1 and 2 fit snugly each within a cell of a cellularinsulating form 22, having the shape of a figure eight, and which servesas a coil form during the winding of the coil 3. The form and shape ofthe latter represents a primary point of novelty in the presentinvention. The coil 3 includes two rounded substantially semi-circularportions 24 and 25, when viewed in plan, joined by rectilinear portions26 and 27. Use of the specially shaped core results in closer couplingbetween the coil 3 and the armatures of the switches 1 and 2, andfurther in the reduction of the total copper employed in the core. Thelatter result flows from the shape of the coil, which inherentlycontains less copper than would a circular coil, but also from the factthat closer coupling with the armatures is accomplished, which enablesuse of a coil of fewer turns, if desired.

In the system of Figures 3, 4 and 5, the novel concept of the system ofFigures 1 and 2 is carried forward to a a. triple switch, suitable foruse in three-phase circuits. Three switches 30, 31, 32 are employed,which are similar in structure to the switch 1, and which are arrangedwith longitudinal axes parallel, and occupying the apices of anequilateral triangle. This configuration results in maximum compactness.

The switches 30, 31, 32 are surrounded by a common actuating coil 34,which includes three arcuate sections 35, 36, 37, each following roughlythe arc of a circle, and established roughly at the apices of anequilateral triangle. The arcuate sections 35, 36, 37 conform closely incurvature to the shape of the envelopes of switches 30, 31, 32. Adjacentarcuate section pairs of the coil 34 are joined by rectilinear sections38, 39, 40, to form a generally triangular coil.

The virtue of the generally triangular coil above described resides inthe fact that closer coupling is attainable with the armatures ofswitches 30, 31, 32, than is possible when utilizing the conventionalcircular coil. The triangular coil is not more difiicult to wind than isa circular coil, and contains less copper for a corresponding number ofturns, and is therefore not only more advantageous operationally, but isalso more economical of fabrication.

In the system of Figure 4 the coil form 41, in which the coil 39 iswound, is fabricated of insulating material, and includes three parallelthin-walled tubes or cells 42, 43, 44, each adapted to fit snugly aboutone of the switches 30, 31, 32. The tubes42, 43, 44 are joined at theirlines of contact and in the adjacent areas 45, and serve to locateaccurately the switches 30, 31, 32, within the coil 34.

In the embodiment of my invention illustrated in Figure 5 of theaccompanying drawings, a coil form 46 is employed which hugs the innerwall of the coil 34, along its entire surface, and thereby serves onlyto space the switches 30, 31, 32 from the inner wall of coil 34. In thisembodiment the envelopes of the switches 39, 31, 32 are in directcontact along three lines, and the coil form 46 is designed to provide asnug fit of the switches therewithin.

While I have described and illustrated specific forms of the inventionit will be clear that variations thereof may be resorted to withoutdeparting from the true scope of the invention as defined in theappended claims.

What I claim and desire to secure by Letters Patent of the United Statesis:

1. A circuit maker and breaker system including a plurality of separateswitch elements, each of said switch elements including a circularcylindrical vitreous envelope, a pair of separated contacts, a pool ofmercury, one of said contacts permanently within said pool of mercury,the other of said contacts located at a predetermined level with respectto the surface of said pool of mercury, means for varying the level ofsaid pool of mercury to a position above and below said other of saidcontacts, said means for varying including an armature located withinsaid vitreous envelope and submersible in said pool of mercury, and acommon actuating coil for all the armatures of said plurality ofseparate switch elements, said common actuating coil including arcuateportions having inner Walls conforming in radius substantially with theouter walls of each of said vitreous envelope, and having portionstangential to and joining said arcuate portions.

2. The combination in accordance with claim 1 wherein said coil isapproximately of triangular shape, having arcuate apices, said vitreousenvelopes located at said apices.

3. The combination in accordance with claim 1 wherein said coil includesonly two substantially parallel substantially rectilinear portions.

4. The combination in accordance with claim 1 wherein said coil includesthree substantially rectilinear portions, making an angle ofsubstantially 60 one with the other.

5. The combination in accordance with claim 1 wherein is provided acellular coil form for said coil, said cellular coil form providing aplurality of circular cylindrical cells, each of said cells arrangedsnugly to accept one of said vitreous envelopes.

References Cited in the file of this patent UNITED STATES PATENTS2,095,604 Larson Oct. 12, 1937 2,113,595 Larson et al Apr. 12, 19382,166,163 Larson July 18, 1939 2,213,100 Cianchi Aug. 27, 1940 2,289,830Ellwood July 14, 1942 2,318,405 Leveridge May 4, 1943 2,397,123 BrownMar. 26, 1946 FOREIGN PATENTS 485,824 Great Britain May 25, 1938

